Whitney Cameronn (Cotten),谋杀计划夫妇の交换寝取らせ a man with a strong affection for his sister-in-law (Peters). When one of her stepchildren dies, it's revealed that the child was poisoned to death. Whitney suspects his sister-in-law committed the murder and is afraid that her other son may be in danger. The film climaxes during an ocean voyage aboard a cruise ship.
